fix(subs): out-of-window charge was a phantom 12h span (4,100 ALL bug)

The tariff-bridge owed amount summed TWO charges — the early-entry gap +
a "late-exit" gap — and the exit gap (outOfWindowGap edge:"exit") always
measured back to the PREVIOUS window close, even for a subscriber still BEFORE
their window. So a car that entered ~30 min early showed ~12h owed (4,100 ALL)
the moment it was looked up, instead of ~100 ALL.

Replace the two-gap sum with a single correct primitive,
minutesOutsideWindow(timeframes, tz, from, to): the minutes within the actual
stay [entry, now] that fall outside the allowed window (covering early entry AND
late exit, bounded by the stay, weekend/off-days free). windowOwedBetween prices
those minutes once as a transient stay (so increments + daily cap apply) against
the tariff in force at entry. Both the exit gate (subscription-flow) and the
booth quote (pay-station) now use this one source of truth — they can't disagree.

Verified on the live occurrence: was 4,100 ALL, now 100 ALL (9 min outside →
one increment). 87 shared tests (6 new regression cases incl. the phantom span).
Build+lint 12/12.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/server/src/subscription-window.ts

@@ -1,6 +1,7 @@
 import { desc, eq, siteConfig, subscriptionPlans, tariffVersions, tariffs, type Db } from "@parking/db";
 import {
   computeFee,
+  minutesOutsideWindow,
   outOfWindowGap,
   type PlanTimeframes,
   type SubscriptionPlan,
@@ -92,3 +93,37 @@ export function windowCharge(
     tariffVersionId: tv.id,
   };
 }
+
+/**
+ * The TOTAL out-of-window charge a subscriber owes for an OPEN occurrence, computed over
+ * the whole stay `[enteredAt, nowISO)` in ONE shot (not entry-gap + exit-gap, which
+ * double-counts and lets the exit gap reach back to a previous day's close). Sums the
+ * minutes parked outside the plan's allowed window and prices them as a single transient
+ * stay of that duration — so the tariff's increments + daily cap apply correctly. Returns
+ * null when the plan has no timeframes / nothing is owed / no tariff to price against.
+ */
+export function windowOwedBetween(
+  db: Db,
+  planVersionId: string | null,
+  enteredAtISO: string,
+  nowISO: string,
+): { amountMinor: number; minutes: number; currency: string; tariffVersionId: string } | null {
+  const plan = planVersionById(db, planVersionId);
+  const timeframes = (plan?.timeframes ?? null) as PlanTimeframes | null;
+  if (!timeframes) return null;
+
+  const tz = timeframes.tz || siteTz(db);
+  const minutes = minutesOutsideWindow(timeframes, tz, enteredAtISO, nowISO);
+  if (minutes <= 0) return null;
+
+  // Price the out-of-window duration as a transient stay (entry→entry+minutes), against
+  // the tariff in force at entry — reproducible, and the daily cap applies.
+  const tv = tariffVersionAt(db, enteredAtISO);
+  if (!tv) return null;
+  const structure = tv.structure as unknown as TariffStructure;
+  const end = new Date(Date.parse(enteredAtISO) + minutes * 60_000).toISOString();
+  const amountMinor = computeFee(enteredAtISO, end, structure);
+  if (amountMinor <= 0) return null;
+
+  return { amountMinor, minutes, currency: tv.currency, tariffVersionId: tv.id };
+}